The present invention relates to an intervertebral disc prosthesis, intended to be substituted for fibro-cartilaginous discs ensuring a bond between the vertebrae of the spinal column.
Various types of intervertebral disc prostheses are known in the prior art. Numerous prostheses, such as for example in the patent application WO 02 089 701 and WO 2004/041129, are constituted in a lower plate and an upper plate forming a sort of cage around a central core. A part of these prostheses enables the upper plate to swivel in relation to the central core and optionally permits the central core to slide in relation to the lower plate. This sliding of the central core in relation to the lower plate allows spontaneous positioning of the core in the ideal position to absorb constraints imposed on the prosthesis, during movements made by the patient wearing the prosthesis. The displacement of the core, co-operating with at least a plate about an uneven surface, enables an inclination between the plates of the prosthesis which facilitates the mobility of the patient wearing the prosthesis. The displacement of the core also prevents it from creeping under load, when subjected to major constraints. A part of these prostheses have osseous anchorage means allowing to attach these prostheses to the vertebrae between which they are intended to be inserted.
However, the size of the vertebrae varies greatly from person to person, for a same vertebra in a given position in the spinal column, but also for a given person depending on the position of the vertebrae in the spinal column between which a prosthesis is intended to be inserted. The intervertebral disc prostheses must be of a suitable size for the vertebrae between which they are intended to be inserted, depending on the person and on the position of these vertebrae in the spinal column. Moreover, depending on the spinal column disorder of the patient wearing the prosthesis, it is sometimes preferable that the prosthesis allows a correction of this disorder. The prostheses can thus be used to correct an inclination defect of the vertebrae, such as, for example, lordosis. To have prostheses that are suitable for as large a majority of cases as possible, many different prostheses with different plate sizes and inclinations must therefore be envisaged. This multiplicity of prostheses has the major inconvenience of high manufacturing costs and high stock levels. In this context, it is beneficial to provide a prosthesis that may be adapted to different sizes of vertebrae while allowing for different inclinations of the plates. Such a prosthesis would reduce stock levels and manufacturing costs.
One object of the present invention is to provide an intervertebral disc prosthesis allowing limited movements of the different pieces of the prosthesis between one another and comprising a core used to restrict its displacement in at least one direction.
This aim is achieved by an intervertebral disc prosthesis comprising at least three pieces including an upper plate, a lower plate, and a movable core at least in relation to a plate, having two anatomic adaptation elements each of which has, on one hand, a surface in contact with a surface of a vertebra and, on the other hand, a surface of which at least a part of has a surface in contact with at least a part of the plate opposite to which the anatomic adaptation element is mounted, the anatomic adaptation elements being fixed onto the plates via fixation means.
In other embodiments, the anatomic adaptation elements include crowns which surround the plates and prolong respectively their upper and lower surfaces to present contact surfaces of the prosthesis with the adjacent vertebrae are larger. In other embodiments, the crowns of the anatomic adaptation elements of various sizes are adapted on the plates in order to adapt them to vertebrae of different sizes.
According to another feature of some embodiments, the anatomic adaptation elements are anatomic plates, which cover the plates and prolong respectively their upper and lower surfaces to present contact surfaces of the prosthesis with the adjacent vertebrae which are bigger than when there are no anatomic adaptation elements, the anatomic plates being of various sizes in various embodiments to adapt the plates to vertebrae of different sizes.
According to another feature of some embodiments, the anatomic adaptation elements act to effectively and symmetrically prolong the upper and lower surfaces respectively of the upper and lower plates to present an equivalent prolongation of these surfaces on the different anterior, posterior and lateral edges of the plates.
According to another feature of some embodiments, the anatomic adaptation elements act to effectively and asymmetrically prolong the upper and lower surfaces respectively of the upper and lower plates to present a bigger prolongation of these surfaces on at least one of the anterior, posterior and lateral edges of the plates than on the other edges.
According to another feature of some embodiments, the upper surface of the core is in contact with at least one part of the lower surface of the upper plate and the lower surface of the core is in contact with at least one part of the upper surface of the lower plate.
According to another feature of some embodiments, at least one part of the surface of at least a plate is concave and complementary with a convex surface of the core with which it is in contact.
According to another feature of some embodiments, at least one part of the surface of at least a plate is plane and complementary with a plane surface of the core with which it is in contact.
According to another feature of some embodiments, male and female cooperation means situated in the vicinity of the edges of at least one plate and the core limit preferably, without excessive friction, the movements in translation of the core relative to the selected plate, according to an axis substantially parallel to selected plate, and limit or suppress the rotational movement of the core relative to the selected plate, about an axis substantially perpendicular to the selected plate.
According to another feature of some embodiments, the dimensions of each male cooperation means are slightly less than those of each female cooperation means so as to allow clearance between the core and the plate in embodiments equipped with these cooperation means.
According to another feature of some embodiments, the dimensions of each male cooperation means are substantially the same as those of each female cooperation means so as to prevent any clearance between the core and the plate equipped with these cooperation means.
According to another feature of some embodiments, the cooperation means of the plate are female cooperation means co-operating with male cooperation means of the core.
According to another feature of some embodiments, the male cooperation means of the core are two blocks situated on the two side edges of the core and the female cooperation means of the plate are four walls situated, in pairs, on each of the two side edges of this plate.
According to another feature of some embodiments, the fixation means of the anatomic adaptation elements on the plates of the prosthesis are reversible and allow changing the anatomic adaptation elements fixed in a movable manner onto the plates of the prosthesis.
According to another feature of some embodiments, the fixation means of the anatomic adaptation elements on the plates consist in fixation means present on the anatomic adaptation elements and complementary with fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the anatomic adaptation elements are fixed onto the plates via, on one hand, contact with at least a part of their surfaces which face at least a part of the plates and, on the other hand, contact of their fixation means with the complementary fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the fixation means of the anatomic adaptation elements on the plates consist in male fixation means present on the anatomic adaptation elements and that cooperate with the female fixation means present on the plates of the prosthesis or inversely.
According to another feature of some embodiments, the female fixation means present on the plates of the prosthesis consist of plane surfaces present on the edges of the plates of the prosthesis.
According to another feature of some embodiments, the female fixation means present on the plates of the prosthesis consist of recesses made in the edges of the other plate of the prosthesis.
According to another feature of some embodiments, the female fixation means present on the plates of the prosthesis consist of recesses made in the edges of the female cooperation means of the plates of the prosthesis.
According to another feature of some embodiments, the female fixation means present on the plates of the prosthesis consist of plane surfaces present on the edges of one of the plates and in recesses made in the female cooperation means of the edges of the other plate of the prosthesis.
According to another feature of some embodiments, the female fixation means present on at least one of the plates of the prosthesis consist of plane surfaces present on at least a first edge of one of the plates and in recesses made in at least a second edge of the plate of the prosthesis, the second edge geometrically facing a first edge of the plate.
According to another feature of some embodiments, at least one of the female fixation means present on the plates of the prosthesis comprises at least a notch allowing blocking the male fixation means of the anatomic adaptation elements on the selected female fixation means.
According to another feature of some embodiments, the fixation means of the anatomic adaptation elements on the plates consist of female fixation means present on the anatomic adaptation elements and co-operating with male intermediary means which can also cooperate with the female fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the anatomic adaptation elements are fixed onto the plates via, on one hand, contact of at least a part of their upper and lower surface with at least a part of respectively the upper and lower plates and, on the other hand, contact of the male intermediary means with the female fixation means present on the anatomic adaptation elements and with the female fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the male intermediary means possess securing means fixing the male intermediary means in a position to cooperate with both the female fixation means of the anatomic adaptation elements and the female fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the male intermediary means consist of a sliding plate in the female fixation means present on the anatomic adaptation elements to cooperate with the female fixation means present on the plates of the prosthesis, the securing means of the male intermediary means consisting of at least an irregularity present on at least one side of the selected plate that cooperates with an opening in the female fixation means of the anatomic adaptation elements and/or in the female fixation means of the plates, thus fixing the male intermediary means in a position where they cooperate with both the female fixation means of the anatomic adaptation elements and the female fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the securing means of the male intermediary means consist of a bore in the male intermediary means and in the female fixation means present on the anatomic adaptation elements, the bore in the female fixation means of the anatomic adaptation elements capable of receiving a securing pin fixing the male intermediary means in the position to cooperate with the female fixation means present on the plates of the prosthesis.
According to another feature of some embodiments, the median planes representing the upper and lower surfaces of each of the anatomic adaptation elements are substantially parallel or form an acute angle, the inclination obtained by such an angle allowing adaptation of the overall shape of the prosthesis to the anatomy of the spinal column and in some embodiments ameliorate inclination defects of the vertebrae of the patient for whom the prosthesis is intended.
According to another feature of some embodiments, the same anatomic adaptation elements may be assembled with different plates whose upper and lower surfaces create different angles.
According to another feature of some embodiments, an angle between the upper surface of the upper plate and the lower surface of the lower plate is imposed by creation of angles between the upper and lower surfaces of the lower plate and/or the upper plate, or by restricting, with the cooperation means, movements of the core about a position imposing an inclination of at least one of the plates.
According to another feature of some embodiments, the same plates are assembled with cores of different thicknesses and/or sizes and/or shapes.
According to another feature of some embodiments, the anatomic adaptation elements comprise movable osseous anchorage elements that are fixed onto the anatomic adaptation elements upon fixing the anatomic adaptation elements onto the plates, inserting the prosthesis between the vertebrae or adjusting the relative position of the different elements of the prosthesis.
According to another feature of some embodiments, the movable osseous anchorage elements of the anatomic adaptation elements consist of at least a plate equipped with notches oriented to resist the removal of the plate once it has been inserted into a vertebra, a far end of the plate bearing a part curved to fold over itself that may interlock as a hook onto an edge of an opening made in the vicinity of the periphery of the anatomic adaptation elements.
According to another feature of some embodiments, the part, curved to fold over itself, of the notched plate of the movable osseous anchorage means of the anatomic adaptation elements in prolonged with a second plate also equipped with notches oriented to resist removal once it has been inserted into the vertebra.
According to another feature of some embodiments, the anatomic adaptation elements comprise movable osseous anchorage elements consisting of at least one winglet that may be inserted in a groove formed in the adjacent surfaces of the vertebrae between which the prosthesis is to be implanted, said winglet comprising notches oriented to resist ejection of the prosthesis outside its housing between the vertebrae, a far end of the winglet bearing a part curved to fold over itself that may be interlocked as a hook onto an edge of an opening made in the vicinity of the periphery of the anatomic adaptation elements.
According to another feature of some embodiments, the winglet further comprises a pin having dimensions adapted to fit preferably tightly, into a groove of the anatomic adaptation elements and/or the plates.